Determination of absorption of vitamin B₁₂ by a double isotope tracer technique

Abstract

A new simple method for the study of vitamin B₁₂ absorption involving the use of two tracers is described. Along with ⁵⁸Co labeled vitamin B₁₂ an unabsorbable marker in the form of ⁵¹Cr labeled chromic oxide is administered to the patients. The ratio of the activities of the two isotopes in the standard is compared with the ratio of the activies of these isotopes in an aliquot of a stool sample collected after 24 or 48 hours. The absorption of labeled vitamin B₁₂ is estimated from the alteration in the ratio of absorbable and unabsorbable isotopes in the stool sample. The method compares well with other methods of estimating vitamin B₁₂ absorption such as Schilling's test, total faecal collection and whole body counting.